The present invention relates to the field of global positioning in general and more particularly, to determining the orientation of a mobile terminal.
Some mobile devices include an electronic magnetic compass, which may be used to generate a magnetic heading that is displayed to a user. Example mobile devices that include a magnetic compass include some global position system (GPS) units and some mobile telephones. The magnetic compass may include a two or three axis magnetic field sensor. When using a two axis magnetic field sensor, the mobile device should be aligned with the earth's horizontal surface while the magnetic field strength is measured, otherwise the accuracy of the resulting magnetic heading can be reduced. Aligning the mobile device with the earth's horizontal surface may not be a convenient requirement to place on a user and/or may limit how the mobile device can be mounted on a vehicle or worn by a user.
The mobile device may include two tilt sensors (e.g., each tilt sensor with one axis) that sense the orientation of the mobile device relative to the earth's surface. Information from the tilt sensors can then be combined with information from the magnetic sensor to provide heading information that may be less sensitive to the orientation of the mobile device.